Identification of P-glycoprotein at the membrane of mast cell secretory granules. An immunofluorescence and protein A-gold electron microscopical investigation.
The presence of P-glycoprotein has been investigated in rat peritoneal mast cells by means of immunofluorescence and immunogold electron microscopy, using the specific monoclonal antibody JSB-1. Immunofluorescence studies showed that the glycoprotein is primarily concentrated in mast cell granules, and little is localized at the plasma membrane. Electron microscope observations revealed a marked accumulation of colloidal gold particles at the granule-coating membranes, whereas decoration of the plasma membrane is much less intense. When mast cells are stimulated to exocytate with compound 48/80, both immunofluorescence and electron microscopy showed concentration of P-glycoprotein reactivity at the plasma membrane level. Indeed, fusion of the granule with the plasma membrane allowed transfer of immunoreactive P-glycoprotein material from the granule-coating membrane to the cell surface membrane. These findings confirmed the presence of P-glycoprotein in mast cells; it is predominantly localized in the granules and is exposed on the cell surface only after exocytosis, suggesting, therefore, a possible physiological role for P-glycoprotein in the secretion of certain mediators.
Crivellato
E
E
Department of Medical and Morphological Researches, University of Udine, Italy.
Travan
L
L
Candussio
L
L
Bartoli Klugmann
F
F
Decorti
G
G
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000378:metabolism*; D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D003594:Cytoplasmic Granules / Q000378:metabolism* / Q000648:ultrastructure; D005089:Exocytosis / Q000187:drug effects; D019085:Fluorescent Antibody Technique, Direct; D007150:Immunohistochemistry; D008297:Male; D008407:Mast Cells / Q000378:metabolism* / Q000648:ultrastructure; D016253:Microscopy, Immunoelectron; D010537:Peritoneum / Q000166:cytology / Q000648:ultrastructure; D051381:Rats; D017207:Rats, Sprague-Dawley; D003189:p-Methoxy-N-methylphenethylamine / Q000494:pharmacology
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D003189:p-Methoxy-N-methylphenethylamine